1. Field of the Invention
Embodiments of the present invention generally relate to coupling devices used to join sections of pipe and more particularly, to improvements in the gaskets used in various pipe coupling devices.
2. Description of Related Art
A common type of pipe coupling device used to join two pipes employs a housing with a C-shaped gasket that is designed to straddle the joint between the pipes. The portions of the gasket that resiliently contact the outer surface of each pipe are often referred to as “sealing lips.” The C-shaped gasket design can provide an effective seal in both vacuum and pressure applications. A cavity created by the inner surface of the C-shaped gasket functions as a pressure reservoir. In positive pressure applications, pressure within the piping system is applied to the internal surfaces of the gasket via the cavity formed by the gasket. This positive pressure increases the force of the sealing lips against the pipe surfaces. In a vacuum environment, the sealing lips are drawn tighter against the pipe surfaces due to the difference in pressure between the piping system and atmospheric pressure.
One benefit of these types of coupling devices is that they allow for limited expansion and contraction of the pipes in the axial direction, while maintaining contact between the sealing lips and each pipe's outside surface. Movement of the gasket relative to the pipe surfaces can also occur with pressure changes in the piping system. Over time, relative movement between the pipes and the gasket can wear the gasket sealing lips, which can result in leaks. One known solution to this problem is to apply a lubricant, such as grease, to the sealing lips during the installation process to reduce wear on the sealing lips. Although this has improved the performance of the gaskets, additional improvements are needed because the grease can be displaced over time thereby allowing the seals to wear. An additional issue with prior art designs is that gaskets can become damaged during installation.